Of the 1232 surveys mailed, there were 695 respondents and 537 clinicians who refused or did not respond, resulting in an overall response rate of 56% (CARN 66%, non-CARN 47%). Of those who responded, 175 were not currently practicing obstetrics, leaving 520 surveys eligible for analysis (313 of 396 from CARN members and 207 of 299 from physicians outside the network), for an estimated response rate from eligible recipients of 49% (520 of 1057), assuming all recipients who did not deliver babies returned a blank survey. Twenty-four of these 520 surveys (13 CARN and 11 non-CARN) were returned incomplete and were analyzed only for the questions that were completed. Respondents did not differ significantly from nonrespondents in terms of age or gender.
There were only two demographic differences between CARN and non-CARN physicians: CARN members were slightly but significantly older and were also more likely to practice in a multispecialty group (). There were no significant differences in responses between CARN and non-CARN physicians to any other question on the survey. The majority of respondents reported practicing general obstetrics and gynecology as their primary specialty, followed by maternal fetal medicine (MFM) specialists, with few practicing obstetrics only. Most respondents practiced in a single-specialty obstetrician-gynecologist partnership or group practice, followed by solo and university practice. Men accounted for 52% of returned surveys. The mean number of years in practice was 18, with the majority of respondents practicing >10 years. Respondents estimated that about 58% of their patients were white, 18% were Hispanic, and 16% were African American on average, and about a third (32%) of their patients received Medicaid for their health coverage. About 1 in 3 respondents (31%) considered their patient population to be at higher than average risk for preterm birth, with an estimated mean rate of preterm labor in those practices of 16% vs. 9% and 6% for practices with average or lower than average estimated risk, respectively (p<0.001). Physicians who reported their patient population was at higher risk for preterm birth also reported significantly higher rates in their patients of a number of risk factors for preterm birth, as well as higher proportions of African American and Hispanic patients and patients eligible for Medicaid ().
Physician Estimates of Percentage of Patients with Risk Factors for Preterm Birth by Physician's Opinion of Relative Risk of Preterm Birth for Patient Population
Late preterm birth knowledge and opinions
A majority of responding physicians reported having read carefully the ACOG Committee Opinion regarding LPTB (19%) or having at least skimmed it (40%). Only 45.2% of respondents correctly defined LPTB as birth between 34 and 36 completed weeks gestation, with another 14.6% answering 34–37 weeks gestation. The other most common responses were 35–37 weeks gestation (6.0%), 32–36 weeks gestation (5.0%), 32–37 weeks gestation (1.5%), and 34–38 weeks (1.3%). Those physicians who had read the Committee Opinion carefully were more likely to define LPTB as either 34–36 or 34–37 weeks gestation (71.0% vs. 62.9% who had skimmed the Committee Opinion and 55.4% who had not read the Committee Opinion, p=0.030). Most responding physicians (87%) answered that they were aware of the evidence about morbidity and mortality of infants born at 34–36 weeks completed gestation (100% of those who had read the Committee Opinion vs. 73% of those who had not, p<0.001). Virtually all respondents were convinced (74%) or somewhat convinced (21%) by the evidence regarding morbidity and mortality of late preterm infants, and most (81%) considered the evidence sufficient to make a clinical judgment. Again, those physicians who had read the Committee Opinion were more likely to be convinced (p=0.024) and to consider the evidence sufficient to make a clinical judgment (p<0.001).
Most respondents agreed (53%) or strongly agreed (23%) that LPTB is a public health problem. Respondents who estimated their patient population to be at above average risk for preterm birth were more likely to agree or strongly agree that LPTB is a public health problem (84%, p<0.001). Those physicians were also more likely to report an increase in LPTB in their practice (55% vs. 42% and 35% for average and lower than average risk patient populations, respectively, p<0.001). Most (72%) also agreed that late preterm infants comprise the majority of U.S. preterm births. Almost all respondents agreed that late preterm infants have increased risk of neonatal intensive care unit (NICU) admission and hospital readmission after birth (96%) compared with term infants. Most respondents believed that the increase in LPTB in the United States is due to complications of multifetal pregnancy (92%), increasing rates of multifetal pregnancy (88%), and increased maternal disorders (81%).
When asked about potential poor outcomes for infants born late preterm, the overwhelming majority of respondents agreed or strongly agreed that infants born late preterm are at increased risk of short-term poor outcomes, such as respiratory distress (96%), thermal instability (95%), hyperbilirubinemia (95%), feeding problems (94%), hypoglycemia (91%), and apnea (84%). More respondents were either neutral or disagreed about the risk of long-term outcomes, such as learning disabilities, behavioral problems at school age, cerebral palsy, long-term disability, ADHD, and mental retardation (). Women were more likely to agree that LTPB increased risk for learning disabilities, attention deficit hyperactivity disorder (ADHD), and cerebral palsy (p<0.01), and all respondents who reported they were convinced by the evidence for increased risk of morbidity and mortality due to LPTB were more likely to agree that LTPB increases the risk for all these conditions (p<0.01). Respondents were more likely to respond that they were convinced by the evidence if they were female (80.6% vs. 68.3%, p=0.012) or if they had read the Committee Opinion carefully (87.1% vs. 72.2% who had skimmed the Committee Opinion and 69.3% who had not read it, p=0.029). These effects appeared to be independent, as there was no sex difference in the likelihood a respondent reported reading the Committee Opinion carefully. When asked separately how concerned they were about mortality and morbidity for late preterm infants, most respondents were concerned about neonatal (73%) and infant (71%) mortality and long-term health problems (84%) in babies born at 34–36 weeks completed gestation. There was no difference between men and women; physicians who had read the Committee Opinion carefully were significantly more likely to be very concerned about these outcomes for infants born late preterm (30.7% vs. 21.3%, p=0.017; 34.1% vs. 18.6%, p=0.002; and 40.9% vs. 26.9%, p=0.003, respectively).
Babies Born Between 34 and 36 Completed Weeks of Gestation Are at Increased Risk of Long-Term Outcomes
Late preterm birth practices
Almost all responding physicians disagreed or strongly disagreed with logistical reasons or convenience as being appropriate for a delivery at <37 weeks completed gestation, including scheduling considerations (97%), patient preference (95.0%), and patients living a great distance from the hospital (87%). Most (>80%) physicians agreed that certain clinical indications (e.g., severe preeclampsia) are valid reasons for a delivery at <37 weeks (). Sizable proportions of the responding physicians also agreed that maternal renal disease, poorly controlled diabetes, oligohydramnios with otherwise normal antenatal testing, multifetal pregnancy, mild preeclampsia, and intrauterine growth retardation (IUGR) with otherwise normal antenatal testing were appropriate clinical indications for early delivery (). These responses did not differ by physician demographics or by the physicians' opinion of their patient population's preterm birth risk.
Clinician Opinion About Whether Clinical Indications Are Appropriate Reasons for Delivery Before 37 Weeks Completed Gestation
When asked if they offer tocolysis to patients in preterm labor at 34–36 weeks gestation, 60% reported that they would (17% always, 24% most of the time, 19% sometime, 24% rarely). Less respondents reported that they offer steroids for fetal lung maturation to patients who are at risk of delivery at 34–36 completed weeks of gestation (7% always, 10% most of the time, 11% sometimes, 30% rarely). Most responding physicians reported that they assess fetal lung maturity before induction or delivery for patients with planned, nonemergent delivery prior to 39 weeks gestation (35% always, 23% most of the time, 14% sometimes, 20% rarely).
Half of the responding physicians reported that concerns about malpractice risks contribute to their decision to induce labor or perform a cesarean section at 34–36 weeks completed gestation (35.0% somewhat important, 15% very important). Over two thirds (69%) reported they have had a patient request to be induced or have a cesarean section before 37 weeks when not medically indicated; however, almost none (3 %) reported that they complied with such a request. The most commonly cited reason for such a patient request was discomfort or fatigue (66%).
Gestational age assessment
Only about a third of respondents (37%) believed that inaccurate gestational age assessment contributes to the increase in LPTB. When asked what methods are routinely used in their practice to assess gestational age, most responding physicians reported that they perform a first trimester ultrasound for gestational age assessment (75%), and slightly more (84%) reported performing a second trimester ultrasound for gestational age assessment. Most respondents chose first trimester ultrasound measurement of crown-rump length as both the most reliable measure of gestational age (85%) and the most useful in their practice (76%). About half of the respondents (48%) reported that an insurance company had denied reimbursement for a first trimester ultrasound for gestational age assessment, and 35% reported that an insurance company had denied reimbursement for a second trimester ultrasound for gestational age assessment. Just over half the respondents (52%) reported that performing a first trimester ultrasound affected reimbursement for a second trimester ultrasound.